After writing about ways to naturally colour soap, I thought I’d better complete the story with a list of natural soap additives that I love. So, how did I decide what goes in the “additive” category and what’s a colourant? There’s definitely some overlap, to be sure. The things on the “additives” list are generally insoluble, so they can act as a bit of an exfoliatant. They also aren’t already on my list of colourants, so while clay can be both, it’s already on the colourant list, so there it will live. It’s hardly a science, but it’ll do. This list is, of course, far from complete, but I think it’s a great starting point, and these are the additives I just keep coming back to.
Flower petals, leaves, and herbs
There’s no shortage of types of botanical bits to toss into a batch of soap, but most go a bit wonky in the colour department. Rose petals go black, and lavender buds take on a brown colour that, when combined with their characteristic shape, make them look like wee bits of mouse poop in your soap. Calendula petals, hower, keep their lovely yellow colour, and as a result are a favourite in soaps. You are, of course, welcome to use whatever botanical bits & pieces you like, just be sure to do a test batch first so you know what’s going to happen in the colour department. I’d also always recommend using the dried version so the petals don’t warp the soap on you as they dry.
Grains are one of my favourite soap additives. They’re easy to come by, inexpensive, and can be ground to a variety of different textures for different levels of scrubby power. Toasted, ground rice and barley are two of my favourites, and are fantastic in Thai and beer soaps, respectively.
Coffee grounds make a fantastically scrubby soap, great for gardeners and other people who love to get their hands dirty. And, best of all, you can use them after you’ve made your coffee with them, so you can avoid excess waste. Just take care not to overdo it on the grounds, and start at about a tablespoon of grounds per 500g/1lb of oils—the first batch of coffee ground soap I made could have been used to scrub off tattoos.
Tea leaves are a fun way to accentuate a tea-themed soap. I would advise you to lightly grind them down in your DIY coffee grinder, though, and to be wary of using too many leaves as the leaves swell up greatly in size when exposed to water. My first batch of tea leaf soap ended up having far larger bits of tea (and as a result, far more tea in relation to the soap) in it than I’d anticipated. The large bits of tea then proceeded to dry out and be quite tough on the skin, and generally refuse to wash down the drain easily.
Nuts & seeds—ground almonds, shredded coconut, other chopped/ground nuts, poppy seeds
As with many soap additives that are quite solid, here’s another category where you’ll want to be sure to be using rather small, well-ground bits of these things, and avoid using too much. My first go at soap using shredded coconut was like a bar of soap combined with steel wool—I used large flake ground coconut, and far too much of it. Ouch! Stick with well ground bits—you’ll notice once the bar is done, I promise.
A whole luffa/loofah is a really fun thing to work into your soaps—learn more about that here. You can also buy ground up luffa and use that as well.
Other soap—scraps, balls, etc.
Working bits of other batches of soaps into new batches can be a fun way to use up scraps, or to work in a neat polka-dot/suspended shape of your choice effect.
And, to close, I should note that a good rule of thumb is 1–2 tbsp of additives per 500g/1lb of oils, taking into consideration the grittiness of the additive, and the intended use of the soap.
Ok, that’s my list—what are your favourites?